It is generally always a goal of aircraft designers to design aircraft mechanical components that are reliable, small-sized, and lightweight. This is particularly true for the various actuators utilized aboard aircraft for moving flaps, ailerons, elevators, and similar surfaces. Usage of actuators of a hydraulic type for such purpose is well-known in the art.
Because of their ability to be constructed in relatively small sizes, the ram/cylinder portions of hydraulic actuators are well-suited for operating aircraft flaps, ailerons, etc., since they may be designed to easily fit within wing surface envelopes. In the past, actuators of this type have been used in combination with a main or centralized hydraulic system aboard an aircraft. In this type of arrangement, the actuators are basically in the form of a cylinder and piston arrangement placed within a lifting surface envelope, with pressurized hydraulic fluid being supplied to the actuators from the main system by a network of fluid conduits. Although individual actuators would be independently operable, each actuator would not be independent from the others in the sense that each actuator must rely on the main system as a source of supply of pressurized hydraulic fluid.
There are at least two disadvantages to the above type of system. One disadvantage is that such a system tends to increase aircraft weight in large aircraft since a relatively complex network of hydraulic conduits is required to supply hydraulic fluid from the main system to the various actuators distributed throughout the aircraft. The other disadvantage is that if the main system should happen to fail, all of the actuators to which the system supplies fluid would become inoperable.
In an effort to overcome these disadvantages, aircraft designers have developed actuators that are independently operable but do not rely on a main or centralized hydraulic fluid system. Such developments have included the development of all-electric actuators wherein all hydraulics are totally eliminated. Other developments have included the development of small-sized hydraulic actuators designed to be independent units. In this latter case, each actuator may have an independent pump for providing pressurized hydraulic fluid. The hydraulic system of each actuator is integrated as part of the actuator so that individual actuators are not dependent on a main system or other actuator systems. Such an isolated unit is commonly called an "Integrated Actuator Package" or IAP. Dowty Rotol, Ltd. of Bristol, Great Britain has been known to develop actuators of this type. The actuator of the present invention is also of this general type, but is not necessarily limited to IAP actuators that are of a small size.
The features and advantages of the present invention will now be explained and will become apparent to the reader after reading the remaining parts of this application.